KR20110000146A - Method for fabricating semiconductor device - Google Patents

Abstract

PURPOSE: A method for manufacturing a semiconductor device is provided to prevent the generation of over-etching related defects by reducing the thickness of an oxide film grown on a poly-silicon film for bit-line contact. CONSTITUTION: An interlayer insulating film(25) is formed on the cell region and the peripheral region of a substrate(20). A bit-line contact hole(26) exposing a part of the substrate in the cell region is formed in the interlayer insulating film. A first poly-silicon film(27A) is formed on the cell region and the peripheral region. A second poly-silicon film is formed on the cell region and the peripheral region. The second poly-silicon film, the first poly-silicon film, and the interlayer insulating film are eliminated. A gate oxide film(28A) is formed in the peripheral region.

Description

Manufacturing method of semiconductor device {METHOD FOR FABRICATING SEMICONDUCTOR DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to reduce the thickness of an oxide film grown on a polysilicon film for a bitline contact, thereby resulting in a thick oxide film on the upper part of the polysilicon film for a bitline contact. The present invention relates to a method of manufacturing a semiconductor device suitable for solving the problems in the.

In DRAM devices, in which a unit cell is composed of one MOS transistor and one capacitor, reducing the area while increasing the capacitance of a capacitor, which occupies a large area on a chip, is highly integrated. Has become an important factor.

In order to form a capacitor having a high capacitance in a small area, attempts have been made to increase the height of the capacitor or to reduce the thickness of the dielectric film.

However, when the height of the capacitor is increased, a problem occurs due to an increase in the level difference due to the increase in the capacitor height, and when the thickness of the dielectric film is decreased, a problem in which the leakage current increases.

In order to overcome this problem, recently, a buried type gate structure is used to reduce the bit line parasitic capacitance by half to dramatically lower the capacitance of the capacitor required to maintain the same sense amplifier capability. This was introduced.

1A to 1F are cross-sectional views illustrating a method of manufacturing a semiconductor device according to the prior art.

Referring to FIG. 1A, the device isolation layer 11 is formed in the cell region CELL and the peripheral region PERI of the substrate 10 to define the active region 10A.

Subsequently, the hard mask layer 12 is formed on the cell region CELL and the peripheral region PERI, and the hard mask layer 12 and the device isolation layer 11 of the predetermined portion of the gate of the cell region CELL are formed by a photolithography process. And etching the substrate 10 to form the trench 13.

Next, the buried gate BG is formed under the trench 13, and the source and drain S and D are formed in the active region 10A on both sides of the trench 13.

Next, the capping layer 14 is formed on the cell region CELL and the peripheral region PERI to fill the trench 13, and the interlayer insulating layer 15 is formed on the capping layer 14.

Next, the bit line contact hole 16 exposing the drain D is formed by patterning the interlayer insulating layer 15, the capping layer 14, and the hard mask layer 12 of the cell region CELL by a photolithography process. The polysilicon film 17 is formed on the entire surface including the bit line contact hole 16.

The polysilicon film 17 is used as a bit line contact electrically connecting the bit line (not shown) and the drain D. The polysilicon film 17 is heavily doped to reduce the bit line contact resistance. poly silicon layer).

Referring to FIG. 1B, the polysilicon layer 17, the interlayer insulating layer 15, the capping layer 14, and the hard mask layer 12 of the peripheral region PERI are removed to remove the substrate 10 of the peripheral region PERI. Expose

Referring to FIG. 1C, a gate oxide film 18A is formed on the substrate 10 of the peripheral region PERI by an oxidation process.

During the oxidation process, the surface portion of the polysilicon film 17 of the cell region CELL is oxidized to form an oxide film 18B on the polysilicon film 17 of the cell region CELL.

Since the thickness of the oxide film grown on the polysilicon film has a property proportional to the doping concentration of the polysilicon film, the thickness of the oxide film 18B grown on the polysilicon film 17 of the highly doped cell region CELL ( D1 is three times or more thicker than the thickness D2 of the gate oxide film 18A grown on the substrate 10 of the peripheral region PERI.

Referring to FIG. 1D, a mask pattern 19 covering a portion of the peripheral area PERI is formed.

Referring to FIG. 1E, the mask pattern 19 is etched using a barrier to remove the exposed gate oxide film 18A.

At this time, the oxide film 18B of the cell region CELL which is not masked by the mask pattern 19 is also etched. However, since the oxide film 18B is three times thicker than the gate oxide film 18A, the oxide film 18B remains thick on the polysilicon film 17 even after the etching process.

Referring to FIG. 1F, the gate pattern thin film 30A and the oxide thin film 30B having a thin thickness are formed in the peripheral region PERI and the cell region CELL, respectively, by removing the mask pattern 19.

As a result of this process, a thick gate oxide film having a structure in which the gate oxide film 18A and the gate oxide film 30A are stacked is formed in a portion of the peripheral region PERI, and the thin gate oxide film composed of only the gate oxide film 30A is formed in the remaining portion. Is formed. That is, a gate oxide film having a dual structure is formed in the peripheral region PERI.

Subsequently, although not shown, a gate conductive layer (not shown) used as a gate electrode of a transistor formed in the peripheral region PERI is formed on the cell region CELL and the peripheral region PERI, and the interlayer insulating layer 15 is formed. A chemical mechanical polishing (CMP) process is performed to expose the bit line contacts in the bit line contact holes 16.

However, the above-described prior art has the following problems.

The thick oxide film 18B grown on the polysilicon film 17 in the cell region CELL remains after the subsequent etching process, and is separated between the bit line contacts due to the oxide film 18B during the CMP process for forming the bit line contact. Is not properly made, resulting in a failure that the adjacent bit line contacts are shorted.

Meanwhile, in order to prevent the short between the bit line contacts, the thickness of the oxide layer 18B must be reduced before the CMP process for separating the bit line contacts, and for this purpose, the etching process is excessively performed during the etching process illustrated in FIG. 1E. However, if the etching is excessively performed, the device isolation layer 11 of the peripheral region PERI is attacked and the height of the device isolation layer 11 is lowered, and the top corner portion of the device isolation layer 11 is turned off downwards. The threshold voltage of the semiconductor device formed in the PERI is distorted.

The present invention is a method for manufacturing a semiconductor device suitable for solving the problem in the subsequent process caused by the thick oxide film on the upper part of the polysilicon film for bit line contact by reducing the thickness of the oxide film grown on the polysilicon film for bit line contact To provide.

A method of manufacturing a semiconductor device according to an embodiment of the present invention includes forming an interlayer dielectric layer on a cell region and a peripheral region of a substrate, and forming a bit line contact hole exposing a portion of the substrate of the cell region in the interlayer dielectric layer; Filling the bit line contact hole by forming a first polysilicon layer on the cell region and the peripheral region, and second polysilicon having a slower oxidation rate than the first polysilicon layer on the cell region and the peripheral region Forming a film, removing the second polysilicon film, the first polysilicon film, and the interlayer insulating film formed in the peripheral region, and removing the second polysilicon film in the cell region and the substrate surface of the peripheral region. Oxidizing to form an oxide film in the cell region and forming a gate oxide film in the peripheral region.

The first polysilicon film is formed of a doped polysilicon film.

The second polysilicon film may be formed of a doped polysilicon film doped at a lower concentration than the first polysilicon film.

The second polysilicon film is formed of an undoped polysilicon film.

The second polysilicon film is formed of a crystalline polysilicon film.

The crystalline polysilicon film is formed by depositing an undoped polysilicon film at a predetermined temperature or more.

The crystalline polysilicon film is formed by crystallizing the surface of the first polysilicon film by a heat treatment process.

After forming the oxide film and the gate oxide film, forming a mask pattern covering a portion of the peripheral region, removing the oxide film and the gate oxide film using the mask pattern as a barrier, and removing the mask pattern. And forming the oxide thin film on the cell region and forming the gate oxide thin film on the peripheral region in a unit cycle process, repeating the unit cycle process at least one time. .

After the step of repeating the unit cycle process, forming a gate conductive film on the cell region and the peripheral region, and the gate conductive film and the first polysilicon film to expose the interlayer insulating film of the cell region And etching the entire surface to form a bit line contact in the bit line contact hole.

The second polysilicon film is formed to a thickness of 1/2 to 1 times the thickness of the gate oxide film.

According to the present invention, since the thickness of the oxide film grown on the polysilicon film for the bit line contact is reduced, due to the thick oxide film on the upper part of the polysilicon film for the bit line contact, the bit line is not properly separated during the bit line contact separation process so that adjacent bit lines are not formed. The problem of shorting can be solved.

In addition, the thickness of the acid ™ film grown on the polysilicon film for the bit line contact is reduced so that there is no need to perform excessive etching during the subsequent gate oxide etching process. Therefore, it is possible to prevent device defects due to loss of the device isolation layer in the peripheral region due to excessive etching.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2A through 2F are cross-sectional views illustrating a method of manufacturing a semiconductor device in accordance with an embodiment of the present invention.

Referring to FIG. 2A, the device isolation layer 21 is formed in the cell region CELL and the peripheral region PERI of the substrate 20 to define the active region 20A.

Subsequently, the hard mask layer 22 is formed on the cell region CELL and the peripheral region PERI, and the hard mask layer 22 and the device isolation layer 21 of the predetermined region of the cell region CELL gate are formed by a photolithography process. And etching the substrate 20 to form the trench 23.

The hard mask film 22 may be formed of a nitride film or a stacked structure of an oxide film and a nitride film.

Next, the buried gate BG is formed under the trench 23, and the source and drain S and D are formed in the active region 20A on both sides of the trench 23.

The buried gate BG forms a gate insulating film along the surface curvature on the substrate 20 including the trench 23, forms a metal film on the gate insulating film to fill the trench 23, and then covers the metal film and the gate insulating film on the entire surface thereof. It may be formed by etching.

Subsequently, the capping layer 24 is formed on the cell region CELL and the peripheral region PERI to fill the trench 23, and the interlayer insulating layer 25 is formed on the capping layer 24.

The capping layer 24 is to prevent oxidation of the metal layer used as the buried gate BG, and may be formed of an oxide layer or a nitride layer.

After forming the capping layer 24 and before forming the interlayer insulating layer 25, a planarization process may be performed to planarize the surface of the capping layer 24.

Next, the bit line contact hole 26 exposing the drain D is formed by patterning the interlayer insulating layer 25, the capping layer 24, and the hard mask layer 22 of the cell region CELL by a photolithography process. The first polysilicon film 27A is formed on the entire surface including the bit line contact hole 26 to fill the bit line contact hole 26.

The first polysilicon layer 27A is used as a bit line contact electrically connecting the bit line (not shown) and the drain D. The first polysilicon layer 27A is heavily doped with polysilicon to lower the resistance of the bit line contact. It is formed into a film.

Subsequently, a second polysilicon film 27B having a slower oxidation rate than the first polysilicon film 27A is formed on the first polysilicon film 27A.

The second polysilicon film 27B may be formed of either an undoped polysilicon film, a doped polysilicon film doped at a lower concentration than the first polysilicon film 27A, or a crystalline polysilicon film.

The crystalline polysilicon film may be formed by depositing an undoped polysilicon film at a predetermined temperature, for example, 550 ° C. or more, or by crystallizing the surface of the first polysilicon film 27A by a heat treatment process.

Here, when the thickness of the second polysilicon film 27B is relatively thin, the thickness of the first polysilicon film 27A is relatively low, so that the conductivity is low, and when the thickness of the second polysilicon film 27B is thin, the second polysilicon film 27B is formed during the subsequent oxidation process. Not only the 2 polysilicon film 27B but also the first polysilicon film 27A having a fast etching speed thereunder is oxidized, so that the thickness of the oxide film 28B (see Fig. 2C) becomes thick.

Therefore, the thickness of the second polysilicon film 27B is configured in such a range that the thickness of the oxide film 28B grown in the cell region CELL can be minimized while minimizing a drop in conductivity. For example, the thickness of the second polysilicon layer 27B may be 1/2 to 1 times the thickness of the gate oxide layer 28A formed in the peripheral region PERI.

Referring to FIG. 2B, the second and first polysilicon layers 27B and 27A, the interlayer insulating layer 25, the capping layer 24, and the hard mask layer 22 of the peripheral region PERI may be removed. The substrate 20 of PERI is exposed.

Referring to FIG. 2C, a gate oxide film 28A is formed on the substrate 20 of the peripheral region PERI by an oxidation process.

In the oxidation process, the second polysilicon film 27B of the cell region CELL is oxidized to form an oxide film 28B in the cell region CELL.

Since the second polysilicon film 27B has a slower oxidation rate than the first polysilicon film 27A, the thickness T1 of the oxide film 28B is reduced as compared with the prior art.

Referring to FIG. 2D, a mask pattern 29 covering a portion of the peripheral area PERI is formed.

Referring to FIG. 2E, the mask pattern 29 is etched with a barrier to remove the exposed gate oxide layer 28A.

As the etching process, a wet etching process or a dry etching process may be used.

In the etching process, the oxide layer 28B of the cell region CELL is also etched. Since the thickness of the oxide film 28B is not thick unlike the prior art, almost all of the oxide film 28B is removed during the etching process.

Referring to FIG. 2F, the mask pattern 29 is removed to form a gate oxide thin film 40A and an oxide thin film 40B having a thin thickness in the peripheral region PERI and the cell region CELL, respectively.

As a result of this process, a thick gate oxide film made of a gate oxide film 28A and a gate oxide film 40A is formed in a portion of the peripheral region PERI, and a thin gate oxide film made of only the gate oxide film 40A is formed in the remaining portion. . That is, a gate oxide film having a dual structure is formed in the peripheral region PERI.

Meanwhile, in the exemplary embodiment shown in the drawing, only the case in which the gate oxide layer of the peripheral region PERI is formed in a dual structure is illustrated, but the thickness of the peripheral region PERI gate oxide layer may be three or more branches.

To this end, forming the gate oxide layer 28A, forming the mask pattern 29, removing the gate oxide layer 28A exposing the mask pattern 29 as a barrier, and removing the mask pattern 29 The removing may be repeated at least twice while varying an area opened by the mask pattern 29.

Next, the surface of the gate oxide thin film 40A may be nitrided by a plasma nitridation process.

Subsequently, a conductive film for a gate electrode (not shown) for use as a gate electrode of the peripheral region PERI is formed on the cell region CELL and the peripheral region PERI, and the entire surface is etched so that the interlayer insulating layer 25 is exposed. The process is performed to form a bit line contact isolated inside the bit line contact hole 26.

An etchback process or a CMP process may be used as the front surface etching process.

At this time, only the oxide thin film 40B exists between the first polysilicon film 27A in the cell region CELL and the conductive film for the gate electrode. Since the thickness of the oxide thin film 40B is very thin, the influence of the oxide thin film 40B on the entire surface etching process is negligible. Therefore, a defect in which the bit line contacts are not separated during the front surface etching process does not occur.

As described in detail above, problems in subsequent processes caused by a thick oxide film on the polysilicon film for bit line contact by reducing the thickness of the oxide film grown on the polysilicon film for bit line contact (bitline contact Between the short and the isolation layer attack in the peripheral region can be solved.

In the detailed description of the present invention described above with reference to the embodiments of the present invention, those skilled in the art or those skilled in the art having ordinary knowledge in the scope of the present invention described in the claims and It will be appreciated that various modifications and variations can be made in the present invention without departing from the scope of the art.

1A to 1F are cross-sectional views illustrating a method of manufacturing a semiconductor device according to the prior art.

2A through 2F are cross-sectional views illustrating a method of manufacturing a semiconductor device in accordance with an embodiment of the present invention.

<Description of main parts of drawing>

20: substrate

25: interlayer insulating film

26: bit line contact hole

27A, 27B: first and second polysilicon films

28A: gate oxide

28B: oxide film

40A: gate oxide thin film

Claims (10)

Forming an interlayer dielectric layer on the cell region and the peripheral region of the substrate and forming a bit line contact hole in the interlayer dielectric layer to expose a portion of the substrate of the cell region; Filling a bit line contact hole by forming a first polysilicon layer on the cell region and a peripheral region; Forming a second polysilicon film having a slower oxidation rate than the first polysilicon film on the cell region and the peripheral region; Removing the second polysilicon film, the first polysilicon film, and the interlayer insulating film formed in the peripheral region; And Oxidizing a second polysilicon film in the cell region and the substrate surface in the peripheral region to form an oxide film in the cell region and forming a gate oxide film in the peripheral region; Method of manufacturing a semiconductor device comprising a. The method of claim 1, The first polysilicon film is a semiconductor device manufacturing method, characterized in that formed of a doped polysilicon film. The method of claim 1, And wherein the second polysilicon film is formed of a doped polysilicon film doped at a lower concentration than the first polysilicon film. The method of claim 1, And the second polysilicon film is formed of an undoped polysilicon film. The method of claim 1, And the second polysilicon film is formed of a crystalline polysilicon film. The method of claim 5, The crystalline polysilicon film is a method of manufacturing a semiconductor device, characterized in that formed by depositing an undoped polysilicon film at a predetermined temperature or more. The method according to claim 1 or 5, And the crystalline polysilicon film is formed by crystallizing the surface of the first polysilicon film by a heat treatment process. The method of claim 1, After the oxide film and the gate oxide film are formed, Forming a mask pattern covering a portion of the peripheral area; Removing the oxide layer and the gate oxide layer using the mask pattern as a barrier; Removing the mask pattern; and Forming an oxide thin film on the cell region and forming a gate oxide thin film on the peripheral region; In a unit cycle process, Repeating the unit cycle process at least once; Method of manufacturing a semiconductor device comprising a. The method of claim 8, After repeating the unit cycle process, Forming a gate conductive film on the cell region and the peripheral region; And Forming a bit line contact in the bit line contact hole by etching the entire surface of the gate conductive layer and the first polysilicon layer to expose the interlayer insulating layer of the cell region; Method of manufacturing a semiconductor device comprising a. The method of claim 1, And the second polysilicon film is formed to a thickness of 1/2 to 1 times the thickness of the gate oxide film.

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